Improved methods for the purification of alpha 1-antitrypsin, antithrombin III, and alpha 2-macroglobulin from normal human plasma will be developed and the characterization of these proteins will be continued. In particular, the reactivities of these inhibitors with various seryl proteases will be investigated in an attempt to define the physiological role of the inhibitors in vivo. Direct measurement of the surface excess concentration of human plasma HDL(alpha)- and LDL(beta)-lipoproteins, human serum albumin, bovine insulin, and other model macromolecules (modified by reaction with 3H-, 14C- or 35S-labeled reagents) will be conducted, and the results will be compared with surface excess concentrations obtained by application of the Gibbs' Adsorption Isotherm to measurements of dynamic surface tension (pendant drop method). BIBLIOGRAPHIC REFERENCES: L.A. Learned, J.W. Bloom, and M.J. Hunter, The Antithrombin Activity of Antithrombin III, Thrombosis Research 8, 99-109 (1976). W. Scheider, H.M. Dintzis and J.L. Oncley, Changes in the Electric Dipole Vector of Human Serum Albumin due to Complexing with Fatty Acids, Biophys. J. 16, 417-431 (1976).